This proposal will focus on characterization of T lymphocytes in arthritis. These studies will draw upon our original observation that synovitis in patients with rheumatoid arthritis (RA) is characterized by the presence of "dominant" T cell clones which can be identified in Southern blot analyses using a probe for the C- beta regions of the T cell antigen receptor (TCAR). By identifying the T lymphocytes which correspond to these dominant clones, we will proceed to cloning of the alpha and beta genes of the TCAR as a means for determining whether there is selective V gene expression in common among RA patients. Populations of T lymphocytes will be selected from synovial tissue and propagated in interleukin 2 to obtain sufficient numbers of cells to evaluate the phenotype and T cell receptor gene rearrangement of lymphocytes derived from the site of joint destruction. In addition, monoclonal against the TCAR, including anti-variable regions and anti-idiotypic antibodies, will be produced as a means for identifying the dominant clones in the original tissues and for detection of possible TCARs in common among RA patients. Synovial tissue-infiltrating lymphocytes will be compared to blood and synovial fluid-derived lymphocytes in order to gain perspective on the distribution of the lymphocytes involved in the inflammatory process. Further characterization of lymphocytes from inflamed synovia will include assessment of possible antigenic specificities. The observation that there is an in vivo selection for "dominant" clones of T lymphocytes at the site of inflammation will permit us to devise strategies for identifying the antigens being recognized and to produce therapeutic reagents targeting these disease-related lymphocytes. These studies are central to questions of in vivo selection of the immune repertoire in inflammatory processes, including auto-immune diseases where tolerance-breaking T lymphocyte clones could be pathogenic.